Ink cartridges used in inkjet printers include a printhead and one or more chambers that hold the ink. The printhead is a micro-electromechanical part that contains an array of miniature thermal resistors or piezoelectric transducers that are energized to eject small droplets of ink out of an associated array of orifices. The cartridge is mounted in a carriage in the printer and electrically connected to the printer controller. Under the direction of the controller, the cartridge is scanned back and forth across the print medium (usually paper) as resistors or transducers are energized to eject droplets of ink through the orifices on to the medium in the desired pattern.
In many conventional ink cartridges, each ink chamber is filled with a block of foam to hold the ink and to generate backpressure that helps regulate the flow of ink to the printhead. The ink-holding capacity of full blocks of foam that fill the ink chamber, however, is not always fully utilized. Full blocks of foam can also generate too much backpressure, stranding ink in the cartridge. The cost of the foam is a significant part of the overall cost of the ink cartridge.